This invention relates to a motor vehicle seat belt retractor and particularly to a retractor which can be operated both as an emergency locking retractor or an automatic locking retractor.
Most motor vehicles are equipped with seat belt systems which act to restrain the occupants when the vehicle is subjected to high rates of deceleration which may occur, for example, during a motor vehicle collision. Many seat belt retractors are of the so-called "emergency" locking variety. These retractors employ an inertia sensitive actuator which prevents seat belt webbing from being withdrawn from the retractor when the vehicle is subjected to deceleration forces above a predetermined level, thereby restraining the vehicle occupant. During normal operating circumstances, however, the seat belt webbing may be freely withdrawn from the retractor, enabling freedom of movement by the vehicle occupants.
Another type of seat belt retractor is often referred to as an "automatic" locking retractor. When using these retractors, the seat belt webbing is fully withdrawn from the retractor and, as webbing is thereafter retracted within the retractor, a locking bar engages sprockets within the retractor thus preventing withdrawal. These retractors therefore, act as a one-way clutch once the webbing is fully withdrawn, permitting webbing to be retracted within the retractor but not withdrawn. When, however, the seat belt is unfastened and the webbing is fully retracted within the retractor, the webbing can again be withdrawn.
The emergency locking retractor design has many advantages in terms of occupant comfort and convenience, since they permit free movement of the occupants until deceleration forces above a predetermined level are sensed. Emergency locking retractors, however, have been found undesirable when used to fasten a child restraint system within the vehicle. For this application, it is desirable that the seat belt system firmly and securely anchor the child restraint system to the vehicle. Since automatic locking retractors do not permit free withdrawal of webbing, they are preferable for anchoring a child restraint system within the vehicle.
Due to the need to provide adult occupant comfort and convenience, and the need to securely fasten child restraint systems within vehicles, it is desirable to provide a combination seat belt retractor which may be converted between emergency locking operation and automatic locking operation in accordance with the needs of the user. It is therefore a principal object of this invention to provide such a combination seat belt retractor. It is a further object of this invention to provide a combination emergency locking and automatic locking retractor which is easily switched between operational modes. It is yet another object of this invention to provide a combination seat belt retractor which is simple in design and inexpensive. It is yet another object of this invention to provide a combination retractor having an automatic locking mechanism which is independent of the emergency locking inertia actuator, thereby not adversely affecting the reliability of the emergency locking feature of the retractor.
The above principal objects of this invention are achieved by providing an emergency locking retractor having a pivotable cam member acting on a cantilevered spring member. Pivotable movement of the cam member in one direction moves the spring member for directly biasing the retractor locking bar against the toothed sprockets of the retractor spool, thereby causing the retractor to operate in an automatic locking mode. The retractor according to this invention further includes a switching lever which pivots the cam member for moving the spring member so as to bias the locking bar to the automatic locking position when the seat belt webbing is fully withdrawn from the retractor. The retractor is designed such that when the spool is nearly fully wrapped with seat belt webbing, the webbing acts on the pivotable cam member to pivot the cam member in a second direction for moving the cantilevered spring member until it no longer biases the locking bar, thus returning the retractor to emergency locking operation.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.